The invention relates to a dishwashing machine with a washing compartment and devices for washing dishes using a washing solution as well as with a sorption drying device which is connected to the washing compartment in an air-conducting manner and which comprises a heater as well as a sorption column containing reversibly dehydratable material, the sorption column being arranged inside a housing having an air inlet and an air outlet.
According to DE 103 53 774 and/or DE 103 53 775 of the applicant, reversibly dehydratable material for desorption is heated to very high temperatures. In this case the liquid stored in the material escapes as hot water vapour. The water vapour is conducted into the washing compartment by the conduction of air through the sorption column and a pipe provided, if necessary, and the air in the washing compartment is also heated. The introduction of the hot water vapour and the heated air into the washing compartment during a partial programme step with washing solution to be heated in the processing space is not sufficient for adequate heating of the washing solution and/or the dishes. Further heating may, if necessary, be largely dispensed with and the energy used for desorption can be used almost entirely for heating the washing solution and/or the dishes, except for the energy required to overcome the binding forces between the water and reversibly dehydratable material. Besides a saving of energy, efficient cleaning of the items to be washed is therefore guaranteed.
EP 0 358 279 B1 discloses a device for drying dishes in a domestic dishwashing machine in which the washing solution is heated by a heater arranged outside the washing compartment, preferably an electric geyser, a largely closed drying system being provided in which air circulates from the washing compartment via a drying device that can be regenerated by heating and from this device back into the washing compartment. In this case the drying device consists of a drying compartment that is in thermal contact with the heater, which compartment is filled with a drying means that absorbs the moisture. Because of the connection of the drying compartment to the heater that is provided anyway for heating the washing solution, the drying device is immediately operational after completion of the washing process. The drying means is here placed at least in part as a jacket around the heating elements of the heater so that the drying means in the drying compartment can be heated and hence dried during each heating process.
The drying compartment is designed as a double-wall hollow cylinder into which the drying material is inserted. The inlet and outlet openings for connection to the closed air system are arranged diagonally opposite one another. The disadvantage of this is that there is a relatively high flow resistance, so that the fan provided for promoting the air flow must be operated at very high power. This has a negative effect in terms of noise development and energy consumption.
Because of the structural design of the sorption drying device, which requires inhomogeneous introduction of heat into the drying material, the desorption is time consuming and may also lead to local overheating of the drying means and hence to its irreversible damage. The desorption is also difficult because the heater is arranged in the centre of the double-wall hollow cylinder and radial distribution of heat to the drying means close to the outer hollow cylinder wall is hardly possible because of the air flowing axially past it.